The discovery of presenilins as ubiquitous intramembrane proteases in metazoans exemplifies an emerging trend in biology. The traditional distinction between basic and applied research has become increasingly blurred, as studies initiated with a strictly disease-oriented focus uncover fundamental biological mechanisms. In this renewal application, ten investigators who have collaborated successfully during the last decade on the normal and pathological biology of presenilin (PS) wish to extend their productive interactions into new experiments that will further illuminate the structure-function relationships of PS/ ? -secretase in normal biology and the role of this unusual multi-protein complex and various related gene products in the genesis of Alzheimer's disease. Based on extensive preliminary data in each of our four interrelated projects and supported by three vital cores, we will pursue numerous Specific Aims that include: 1. attempting to determine the structure of PS/ ?-secretase by performing cryo-electron microscopy of the purified, active complex as well as x-ray crystallography of the individual components;2. extending our recent discovery that cholesterol dramatically enhances the catalytic activity of purified ? -secretase and that membrane lipids in general appear to represent the most potent regulators of both A[unreadable] production and Notch cleavage;3. performing extensive genomic, functional genetic and protein analyses searching for novel lateonset AD candidate genes potentially implicated in presenilin-related pathways;4. using advanced microscopy approaches in living cells (bimolecular fluorescence complementation;FLIM) to image and quantify the conformations and interactions of presenilin with APP, with new candidate genes emerging from (2), and with lipids and ? -modulating compounds identified herein;5. identifying common binding partners and common subcellular processing pathways for the (32 subunit of NaJ, APP and APLP2, three proteins that are processed identically by both (3- and y-secretase. 6. performing an unbiased proteomics screen to more fully define the " ? -secretome", i.e., the extent of unknown ?-substrates. These and numerous additional aims and sub-aims will be pursued collaboratively across our 4 projects, with progress in one project modifying experimental plans in another. In short, we are anxious to continue our close interaction to bring greater clarity to exactly how PS and its associated proteins and lipids process a host of substrates within membranes in health and disease. Lay summary: Ten experienced scientists who have collaborated productively for the past decade wish to address the structure and the functions of an unusual protein-cutting enzyme that is required for life in all multi-cellular animals and implicated in the causation of Alzheimer's disease. PRINCIPAL INVESTIGATOR: Dr. Selkoe has been associated with the Harvard Medical School (HMS) since 1972, first as a resident in Neurology and, since 2001, as the Vincent and Stella Coates Professor of Neurologic Diseases at HMS. He is renowned as a pioneer and leader in the field of Alzheimer's Disease research, having made contributions fundamental to several aspects of AD molecular pathogenesis and to the preclinical development of novel treatment strategies for the disease. His work has been recognized by many awards and honors, including LEAD and Merit Awards from NIA, MetLife, Potamkin and Pioneer Awards, and numerous distinguished lectureships. In recent years, his work has centered on mechanisms of amyloid processing, expression, and catabolism. Dr. Selkoe's focus has expanded to include the molecular biology of presenilins, His laboratory is a national and international center for research and training of pre- and post-doctoral students, many of whom have gone on to productive careers in neuroscience research. In this proposal, Dr. Selkoe has brought together much of the top Alzheimer's talent at HMS in collaborative projects. His leadership is evident in the successful evolution of the Center for Neurologic Diseases, of which he is co-director, and his direction and growth of the current program project. He is eminently qualified to lead this program. REVIEW OF INDIVIDUAL COMPONENTS CORE A: ADMINISTRATIVE AND EDUCATIONAL CORE, DR. DENNIS SELKOE DESCRIPTION (provided by applicant): The Administrative and Educational Core will continue to play a key role in the program, integrating the activities of this highly interactive consortium of 4 independent labs and 3 core units (comprised of more than 25 scientific personnel) at the Massachusetts General Hospital and Brigham and Women's Hospital. The 10 co-investigators of the program are strongly committed to enhancing scientific collaboration, communication and education, as we have done during the two preceeding terms of this Program. In this regard, we have found the three specific forums proposed in this core to have been highly effective tools in the previous funding periods. They are therefore included in this renewal of Core A as a means of achieving the important goals of scientific cooperation and exchange that define a NIH Pogram Project Grant. 1) Regularly scheduled Project Leaders'Meetings, attended by all the Project Pi's, their coinvesigators, the Leaders of Core B and C and and selected project scientists, provide ongoing opportunities to examine new developments in each of the 4 projects, and to review one or more of the projects in depth at each meeting, with analysis of progress and problems. 2) Our superb Scientific Advisory Board will continue to consult with the program scientists on an ad hoc basis throughout the year and then convene for an intensive annual on-site review of major new developments in each of the projects. 3) Our successful Seminar Series "Basic and Applied Biology Relevant to Neurodegeneration" will soon enter its 9th year, presenting local and out-of-town speakers, including our own investigators, who inform the Program members and the Boston scientific community at large of new developments in presenilin biology, the pathogenesis of AD and numberous relevant basic research issues. In addition to running the program's vital educational and information-sharing activities, Core A will, as before, manage all the day-to-day fiscal and administrative issues related to our large multi-site program, including regular income/expense reports, inter-institutional personnel and reagent exchanges, joint publications, regular exchange of all publications emanting from the grant, preparation of non-competing renewal applications, and timely and efficient communication with the National Institute on Aging.